Mercari Android Developer Interview Questions and Answers

Algorithm to find LCM of all numbers from 1 to n and its time complexity

• Find prime factors of all numbers from 1 to n

• For each prime factor, find the highest power it appears in any number from 1 to n

• Multiply all prime factors raised to their highest power to get LCM

• Time complexity: O(n*log(log(n)))

NoSQL databases are flexible, scalable, and can handle large amounts of unstructured data.

• NoSQL databases are schema-less, allowing for easy and flexible data modeling.

• They can handle large amounts of unstructured data, making them suitable for big data applications.

• NoSQL databases are highly scalable and can easily handle high traffic and large user bases.

• They provide horizontal scalability by distributing data across...read more

The question asks to find the count of words in a dictionary that can be formed by a given number.

• Iterate through each word in the dictionary

• Check if the characters in the word can be formed using the given number

• Increment the count if the word can be formed

Finding lowest common ancestor of two nodes in binary tree

• Traverse the tree from root to both nodes and store the paths in separate arrays

• Compare the paths to find the last common node

• Return the last common node as the lowest common ancestor

• Use recursion to traverse the tree efficiently

To find the merging point of two linked lists

• Traverse both linked lists and find their lengths

• Move the pointer of the longer list by the difference in lengths

• Traverse both lists simultaneously until they meet at the merging point

Reverse a linked list iteratively

• Create three pointers: prev, curr, and next

• Initialize prev to null and curr to head

• Loop through the list and set next to curr's next node

• Set curr's next node to prev

• Move prev and curr one step forward

• Return prev as the new head

The number of rectangles in an MxN matrix can be calculated using a formula.

• The formula is (M * (M + 1) * N * (N + 1)) / 4

• The matrix can be divided into smaller sub-matrices to count the rectangles

• The number of rectangles can also be calculated by counting all possible pairs of rows and columns

The number is 7744.

• The number must end in 00 or 44.

• The square root of the number must be a whole number.

• The only possible number is 7744.

I am a software developer with experience in multiple programming languages and a passion for problem-solving.

• Proficient in Java, Python, and C++

• Experience with web development using HTML, CSS, and JavaScript

• Familiarity with agile development methodologies

• Strong problem-solving and analytical skills

• Passionate about learning new technologies and staying up-to-date with industry trends

Java function to return subnet mask of IP and URL after www.

• Read the file and store IP addresses and URLs in separate arrays

• Use regex to extract subnet mask from IP address

• Use substring to extract URL after www.

• Return subnet mask and URL as separate strings

Inner join returns only the matching rows between two tables, while outer join returns all rows from one table and matching rows from the other.

• Inner join combines rows from two tables based on a matching column.

• Outer join returns all rows from one table and matching rows from the other.

• Left outer join returns all rows from the left table and matching rows from the right table.

• Right outer join returns all rows from the...read more

To find the length of non-looped linked list, we need to traverse the list and count the number of nodes.

• Traverse the linked list using a pointer and count the number of nodes until the end of the list is reached.

• If a loop is encountered, break out of the loop and continue counting until the end of the list.

• Return the count as the length of the non-looped linked list.

Indexes in MySQL are used to improve query performance by allowing faster data retrieval.

• Indexes are created on one or more columns of a table.

• They work by creating a separate data structure that allows for faster data retrieval.

• Indexes can be created using the CREATE INDEX statement.

• Indexes can also be dropped using the DROP INDEX statement.

• Indexes can be used to speed up SELECT, UPDATE, and DELETE statements.

• Indexes ...read more

include_once and require_once are PHP functions used to include files. The difference is in how they handle errors.

• include_once will only include the file once, and will not throw a fatal error if the file is not found

• require_once will also only include the file once, but will throw a fatal error if the file is not found

• Both functions are used to include files that contain functions or variables that are needed in the

Sessions and cookies are both used for maintaining user state, but sessions are server-side and cookies are client-side.

• Sessions store user data on the server, while cookies store data on the client's browser

• Sessions are more secure than cookies because the data is not accessible to the client

• Cookies can be used for tracking user behavior and preferences

• Sessions are typically used for authentication and authorization p...read more

To find missing number in an array of first n numbers.

• Calculate the sum of first n numbers using formula n*(n+1)/2

• Calculate the sum of given array using loop

• Subtract the sum of array from sum of first n numbers to get the missing number

Design a database schema for a chat application with individual and group messaging.

• Create a 'users' table with unique user IDs

• Create a 'messages' table with message IDs, sender and receiver IDs, message content, and timestamp

• Create a 'groups' table with unique group IDs and group names

• Create a 'group_members' table with group ID and user ID to track group membership

• Use foreign keys to link tables together

• Consider inde

SQL query to retrieve all unread messages upon user sign in

• Use a JOIN statement to combine the messages and user tables

• Filter the results to only show messages that have not been read by the user

• Use the user's sign in information to identify which messages are unread

I am excited to join OLX because of its innovative approach to online marketplaces and its commitment to customer satisfaction.

• I am impressed by OLX's user-friendly platform and its ability to connect buyers and sellers from all over the world.

• I am excited to work with a team of talented developers who are passionate about creating cutting-edge technology.

• I believe that OLX's focus on customer satisfaction aligns with ...read more

I have faced difficulties in debugging complex code and managing project timelines.

• Debugging complex code with multiple dependencies

• Managing project timelines with changing requirements

• Working with legacy code and outdated technologies

• Collaborating with team members in different time zones

• Dealing with unexpected bugs and errors

I report to the Technical Lead and am part of the development team.

• I report to the Technical Lead

• I am part of the development team

Our website receives an average of 10,000 unique visitors per day.

• Our website has a steady flow of traffic with a consistent number of unique visitors per day.

• We use Google Analytics to track our web traffic and analyze user behavior.

• Our peak traffic times are during weekdays from 9am to 5pm.

• We have noticed an increase in mobile traffic over the past year.

• Our website's traffic is primarily driven by organic search and

A program to check if a number is a palindrome or not.

• Convert the number to a string

• Reverse the string

• Compare the original and reversed string

• If they are the same, the number is a palindrome

For Snapdeal's shoe section, I would design a DBMS with separate entities for Sports and Casual Shoes.

• Create a main entity for shoes with attributes like brand, size, color, etc.

• Create separate entities for Sports and Casual Shoes with attributes specific to each category.

• Link the Sports and Casual Shoe entities to the main Shoe entity using a foreign key.

• Use indexing and normalization techniques to optimize performanc...read more

DNS servers translate domain names into IP addresses to enable communication between devices on the internet.

• DNS servers act as a phone book for the internet, translating domain names into IP addresses.

• When a user types a domain name into their browser, the browser sends a request to a DNS server to resolve the domain name into an IP address.

• DNS servers operate in a hierarchical system, with root servers at the top, fo...read more

Merge two sorted arrays into one sorted array of larger size

• Create a new array of size m+n

• Compare the last elements of both arrays and insert the larger one at the end of the new array

• Repeat until all elements are merged

• If any elements are left in the smaller array, insert them at the beginning of the new array

• Time complexity: O(m+n)

• Example: arr1=[1,3,5,7,0,0,0], arr2=[2,4,6], output=[1,2,3,4,5,6,7]

To find square root of a number, use Math.sqrt() function in JavaScript.

• Use Math.sqrt() function in JavaScript to find square root of a number.

• For example, Math.sqrt(16) will return 4.

• If the number is negative, Math.sqrt() will return NaN.